Covering Styrofoam With Plaster?
Materials to cover styrofoam

I made a camo housing for a cache made out of styrofoam and I sprayed it with grey spray paint. However, after it dried the styofoam no longer looked like a rectangle but changed shape and now it looks like a meteor. Heh. That is not what I had in mind. I want it to remain rectangular.

What kind of material could I coat styrofoam with? It would have to retain the
intial shape, fill the pock holes, and be water proof.

My new house is covered with styrofoam, a layer of chicken wire, and a layer of stucco. This method is used a lot because 1) it works 2) you can make a lot of different shapes 3) its cheap.
Did I mention it's cheap and it works?

I'd go with fiberglass. You should be able to find fiberglass matts, just cut to the size needed. Mix resin and apply to the foam, lay the mats down, and coat with resin...may need to go a little sanding to get the edges looking good, but should be long lasting, paintable, and weather-proof.

PS, if you actually go this route, ask for more detailed instructions where ever you buy the materials.

I made a camo housing for a cache made out of styrofoam and I sprayed it with grey spray paint. However, after it dried the styofoam no longer looked like a rectangle but changed shape and now it looks like a meteor. Heh. That is not what I had in mind. I want it to remain rectangular.

What kind of material could I coat styrofoam with? It would have to retain the
intial shape, fill the pock holes, and be water proof.

Do you think wall plaster might work?

Thanks!
GeoWomyn_SF_CA (California)

what's wrong with a meteor shaped cache? could be cool. you could call it the "men in black" cache. have people trade nothing but sunglasses.

You paint it first with Elmers glue, you will want to color the glue with a water base food coloring so that you know what part u have painted. After it dries you can paint it with spray paint. The Elmers glur shell will protect the styrafoam from the paint. I learned this years ago in a college stage craft class, we used this technique quite a few times.

Good tip from JonnyVegas!! To fill the voids, try a lightweight, waterbased spackle first. You may also use paper mache over the surface to give it strength. It the theatre, we used a product called areoball (spelling?) to seal styrafoam prior to painting. This was available from plumbing supply houses. A company that deals in 3-D letters (usually of foam) may also have some ideas. Good luck.

A company that deals in 3-D letters (usually of foam) may also have some ideas.

Most sign companies have gotten away from foam letters. One of the problems is bugs trying to hide in them and birds pecking at them. They destroy the letters. Plastic letter are only a little more expensive and last a very last time without the worries.

Many commercial buildings use a fiberglass mesh material over the foam then a layer of stucco then paint it. Foam is a wonderful home for insects to easily burro into--- warm, dark and dry, especially termites, which is why some local building codes do not allow you to use it below grade (Underground). Another thing to conside is the UV from the sun beating down on this and eventually causing it to fall apart. What effect or look are you trying for? Or are you just trying to make your cache weather proof? If you are trying to camouflage the cache, so Muggles can't accidentally find it or to make the cache more of a challenge, I'd leave the meteor look to break up the box outline. If you want to keep the box shape try using an exterior rated latex house paint.

Mix vermiculite, plaster of Paris and water. Pour mixture into a paper container such as milk carton. Wait fifteen minutes. Peel away paper. The "stone" will be soft at this stage. Mold with hands or carve using a spoon. If you want to work further on your carving, store in a sealable plastic bag...but not for too long.
When done modeling, let dry for a few days and coat with any type paint and sealer.

Mix vermiculite, plaster of Paris and water. Pour mixture into a paper container such as milk carton. Wait fifteen minutes. Peel away paper. The "stone" will be soft at this stage. Mold with hands or carve using a spoon. If you want to work further on your carving, store in a sealable plastic bag...but not for too long.
When done modeling, let dry for a few days and coat with any type paint and sealer.

You should have good luck with Fiberglass & resin, just like you'd use on a boat or surf board ~~~~ also it'll take any kind of paint

If you are gonna go with fiberglass, you need to use epoxy based resin, not the cheaper polyester based resin usually used for autobody work and stuff. The polyester resin will eat the foam as well.

Mopar is right. I worked for an epoxy & polyester manufacturer for 12 years and polyester resins will attack foam. Stick with epoxies. About twice the cost, but well worth it. If money isn't a big concern, consider a epoxy putty, like "SuperMend". Two parts, just mix and spread. You can also make your own putty by adding Cabosil to the epoxy resin and hardener. If you use a resin and hardener I recommend about a 6 oz cloth instead of mat. Easier to shape and work with. You can also add pigments to the resins so there is no need to paint (paint is ok, but will chip over time). A good universal coloring additive is the straight base stuff that get's squirted into your base paint to color it at the local paint/hardware sture. Good Luck!

My new house is covered with Styrofoam, a layer of chicken wire, and a layer of stucco. This method is used a lot because 1) it works 2) you can make a lot of different shapes 3) its cheap.
Did I mention it's cheap and it works?

Exactly. That is the typical application for stucco in construction. I would imagine plaster will work too, but I can guarantee stucco will work.

Mix vermiculite, plaster of Paris and water. Pour mixture into a paper container such as milk carton. Wait fifteen minutes. Peel away paper. The "stone" will be soft at this stage. Mold with hands or carve using a spoon. If you want to work further on your carving, store in a sealable plastic bag...but not for too long.
When done modeling, let dry for a few days and coat with any type paint and sealer.
Makes a secret treasure holder that looks like a rock

Quote

how hard is it to get to look like a real rock?

That recipe will make a very heavy fake rock! If its a micro cache I guess it would work but I wouldn't want to lug a large one out into the woods. For a larger, lighter fake rock try the hypertuff.

When I was taking my one and only college art course, we had to make a sculpture of a human torso. We roughes out the shape in styrofoam, and then covered it with pre-mixed spackling compound. It stuck to the foam, and didn't crack if applied in a thin layer. It was necessary to build up the shape in multiple layers. My opus was not very good, and I later used it for target practice, but the fault was not in the medium.